The invention relates to the technical field of nuclear power plant steam generators, and discloses a nuclear power plant steam generator maintenance liquid charging method and a nuclear power plant steam generator maintenance liquid charging apparatus. The apparatus comprises: a demineralized water storage tank, a maintenance liquid storage tank, a desalinated water charging pipeline, a maintenance liquid charging pipeline and a feeding controller, wherein a first feeding pump and a dry path flow meter are arranged on the demineralized water charging pipeline, the feeding controller is connected to the first feeding pump, and detects the switch of the first feeding pump, the feeding controller is connected to the dry path flow meter, and obtains the flow value of the dry path flow meter,a second feeding pump is arranged on the maintenance liquid charging pipeline, and the feeding controller is connected to the second feeding pump, and controls the output stroke of the second feedingpump according to the flow ate and the dilution ratio. Compared with the method and the apparatus in the prior art, the method and the apparatus have the following characteristics that the uniform mixing degree of the maintenance liquid and the demineralized water is increased, and the nitrogen bubbling operation required for the maintenance of the originally designed steam generator is not used,such that the safety during the overhaul is improved while a lot of labor costs and material costs are saved.